Valve arrangement for a cooling system

ABSTRACT

The invention relates to a valve assembly for a cooling system. The cooling system has a container containing liquid nitrogen under pressure which is to be distributed in vapor form to an enclosed space to be cooled. The valve assembly includes a main valve and pressure operated means for operating the main valve which means utilizes the vapor pressure of the nitrogen in the container referred to above. Two auxiliary valves are provided which are actuated in unison in response to temperature changes in the space to be cooled. The auxiliary valves control the application of pressurized nitrogen vapor to the main valve operating means.

finite States ate .Bespersen 1 Oct. 2, 1973 [54] VALVE ARRANGEMENT FOR A000mm; 3,024,809 3 1962 Shaft! .1 l37/5)6.l8

1,293,858 2/1919 Mills 137/6275 1,126,381 1/1915 Brown,.lr. 137/5962[75] lnventor: Hans Jorgen Jespersen. Sonderborg, 965,270 7 1910 Z8118137 5961 Denmark [73] Assignee: Danf0ss A/S, Nordborg, Denmark PrimaryExaminerWilliam F. ODea Assistant ExaminerPaul Devinsky [22] Fled: 1971Attorneywayne B. Easton [21] Appl. No.: 186,610

57 ABSTRACT Foreign Application Priority Data The invention relates to avalve assembly for a cooling 1970 Germany P 20 48 963-8 system. Thecooling system has a container containing liquid nitrogen under pressurewhich is to be distrib- U.S-

l4, uted in apor form to an enclosed space to be ooled 137/596 The valveassembly includes a main valve and pressure Int. Cl. perated means forperating the main valve which 0 Search means utilizes the vapor pressureof the nitrogen in the 596-1, 596, 6275, container referred to above.Two auxiliary valves are 251/235 provided which are actuated in unisonin response to temperature changes in the space to be cooled. The [56]Ref ren Cited auxiliary valves control the application of pressurizedUNITED STATES PATENTS nitrogen vapor to the main valve operating means.

2,116,801 5/1938 Shivers 62/217 3,281,075 10/1966 Smyers, Jr. I 3 Drawmgfigures 3,239,360 4/1964 Dixon 62/64 VALVE ARRANGEMENT FOR A COOLINGSYSTEM The invention relates to a valve arrangement for a cooling systemand comprising a pressure-actuated main valve for supplying refrigerant,particularly liquid nitrogen, and an auxiliary valve which is operatedin dependence upon temperature and is supplied with a pressurizedmedium, in particular the refrigerant itself, the outlet of theauxiliary valve being connected to the pressure pick-off of the mainvalve and to an airexhaust passage.

For cooling container vehicles, trailers and the like it is oftenrequired to provide a cooling system that is independent of an outsidesource of energy. Thus, it is known practice for the compartment to becooled to be provided with a container of liquid nitrogen which issprayed directly into the cold compartment through nozzle pipes independence upon the position of the main valve, when the temperature inthe cold compartment rises. For the purpose of actuating the main valveuse is made of gaseous nitrogen from the same container, the gas beingpassed through the auxiliary valve into the pressure pick-off of themain valve. The position of the auxiliary valve is controlled by atemperature sensor in the cold compartment, and this valve forms a firstflow-restricting point in the control system. Nitrogen may pass into thecold compartment by way of an air-exhaust passage, i.e., a secondflowrestricting point. Thus, in dependence upon the auxiliary valve anintermediate pressure dependent upon the temperature of the coldcompartment is set up between the two flow-restricting points, thisintermediate pressure causing a corresponding opening of the main valveto a greater or less extent.

it has been found that this valve arrangement does not enable therefrigerant to be uniformly distributed in the cold compartment. If themain valve is not fully opened, the liquid nitrogen only reaches some ofthe outlet nozzles, the other nozzles receiving no supply of the gas.The uneven distribution of refrigerant also affects the accuracy ofoperation of the temperature sensor in the cold compartment.Furthermore, relatively long periods are required for adjustment to takeplace; thus, after a door has been opened, quite a long time elapsesbefore the required temperature is reached again. Also, a considerablepart of the refrigerant is often consumed as the operating pressurizedmedium, and this part is therefore not available for the normal work ofcooling.

The object of the invention is to provide a valve arrangement of theinitially described kind in which the refrigerant is always uniformlydistributed over the outlet nozzles, the periods required for adjustmentare shorter, and smaller quantities of pressurized medium suffice foractuating the main valve.

According to the invention, this object is achieved by blocking theair-exhaust passage by means of a valve which operates in a sensecontrary to that of the auxiliary valve and opens when the auxiliaryvalve is closed.

When in this arrangement the auxiliary valve opens, because of theclosed air-exhaust passage, the entire pressure of the pressurizedmedium, i.e., the entire nitrogen-vapour pressure, for instance, obtainsin the container. The main valve is therefore fully opened with theresult that all the nozzles are uniformly supplied with refrigerant. Therequired temperature in the compartment is reached after only a shortperiod. If the auxiliary valve then closes, the air-exhaust valve opensand the pressure in the control system equates with the pressure in thecold compartment. The main valve therefore moves into the closedposition without delay. Continuous loss of pressurized medium isavoided. Only that part of the pressurized medium located between theauxiliary valve and the main valve is lost during each adjustingoperation.

It is advantageous if, during operation in opposite directions, theclosing ranges of the two valves, that is of the auxiliary valve and theair-exhaust valve, overlap. This ensures that the air-exhaust valve isactually closed before the auxiliary valve opens.

Expediently, the auxiliary valve and the air-exhaust valve are adjustedin opposite directions by a common actuating element. The actuatingelement may for example act on a double-armed lever, of which one armmoves the auxiliary valve and the other the air-exhaust valve. In thisarrangement, the actuating element may engage near the pivotal point ofthe lever so that even slight movements of the actuating element lead toadjustment of the valve.

It is particularly advantageous if there is lost motion between the endsof the lever and a drive face on each of the two valves. Overlapping ofthe closing ranges of the two valves can be achieved in a simple mannerwith the help of this lost-motion arrangement.

The spring-biased closure member of at least one valve may bedisplaceable in a sleeve on which the drive face is formed. The requiredlost motion can be readily set if this step is taken.

A further possible way of carrying out adjustment is provided if theactuating element is a spindle with a stop surface which in one of itsand positions bears against an adjustable stop in the common valvecasing. The adjustable stop enables the double-armed lever to be set inthe correct initial position.

In a preferred construction the lever is fitted in a passage connectingthe auxiliary valve and the air-exhaust valve, the actuating element isloaded in known manner on one side by a diaphragm pressure elementconnected to a temperature sensor and on the other by a rated-valuespring, and that end of the actuating element presented to the diaphragmis surrounded by a bellows which tightly seals off the spaceaccommodating the actuating element and communicating with the passageand which has a small area in comparison with the area of the diaphragm.The area of the bellows may be 10 to 12 times smaller than the area ofthe diaphragm for example. Thus, whenever the full control pressureobtains in the connecting passage, this pressure can act only on a smallarea and cannot therefore interfere wih the regulating action.

The space surrounding the bellows is preferably sealed off tightlyagainst the surrounding atmosphere and is filled with gas at a pressurelower than that of the pressurized medium. The gas pressure may also beless than one atmosphere. This arrangement is of advantage in the caseof containers that are exposed to different atmospheric pressures, forexample those containers transported in aircraft. The thermostaticsystem is not adversely affected by these differences in atmosphericpressure.

in a further form of the invention, a flow-restricting passage can leadfrom the outlet side of the main valve to the surrounding atmosphere byway of cavities in the valve which do not form part of the actuatingpressurized medium system or of the controlled refrigerant system. Inthis way, all the cavities of the valve are acted upon by therefrigerant, even though this is not necessary for functional purposes,so that any accumulation of moisture in the valve that could lead to theformation of ice is prevented. Important in this connetion is that therefrigerant used for flushing purposes is taken from the main system andnot from the control system.

In particular, the spindle of the main valve may in known manner beloaded on the one side by a diaphragm pressure unit connected to theauxiliary valve and on the other by a spring, that end of the valvespindle presented to the diaphragm can be surrounded by a bellows whichtightly seals off the space accommodating the spindle and has an areathat is small in comparison with the area of the diaphragm, and thebellows can surround a space which is substantially sealed off from thesurrounding atmosphere and through which the flow-restricting passageextends. If the flowrestricting passage has a flow-restricting pointupstream and downstream of the sealed-off space, the first of whichpoints provides greater restriction than the second, then the pressurein the sealed-off space is only slightly above atmospheric pressure.With the help of the bellows the counter-action, on the diaphragmpressure unit, of the refrigerant to be controlled is re duced to aminimum. The flushing action of the refrigerant prevents theaccumulation of moisture in the space surrounding the bellows.

The invention will now be described in more detail by reference to anembodiment illustrated in the drawing, in which:

FIG. 1 illustrates schematically a transport container fitted with thearrangement of the invention,

FIG. 2 is a longitudinal section through a valve casing whichaccommodates the auxiliary valve and the airexhaust valve, and

FIG. 3 shows a longitudinal section through a main valve.

FIG. 1 illutrates a transport container 1 the interior 2 of which is tobe cooled. For this purpose, there is provided a container 3 with liquidnitrogen 4 therein which is under the pressure of the nitrogen vapour 5.A pipe 6 runs from the nitrogen container through a main valve 7 to adistributing pipe 8. This is fitted with nozzles 8a from which liquidnitrogen is sprayed into the compartment 2 when the valve 7 is openedand vaporizes in said compartment to produce cold.

The main valve 7 is actuated by a pressure pick-off 7a which may beacted upon by nitrogen vapour by way of a control pipe 9 when anauxiliary valve 10 is opened. This auxiliary valve is opened by anactuating device II in dependence upon a compartmenttemperature sensor12. Connected to the control pipe 9 is an air-exhaust pipe 13 with anair-exhaust valve 14. This valve is closed when the auxiliary valve 10is open, and is opened when the auxiliary valve 10 is closed.

Consequently, either the full nitrogen pressure or the pressure of thecompartment 2 obtains in the control pipe 9. The main valve is thereforeeither closed or fully opened. It merely has an on-off function. Whenthe main valve 7 is opened, the flow-restricting effect is so slightthat liquid nitrogen reaches the last nozzle 80 along the distributingpipe 8.

FIG. 2 shows a casing 15 which accommodates the auxiliary valve 10 andthe air-exhaust valve 14. A bore 16 leads to a connecting port which isconnected to the vapour compartment of the container 3. A bore 17 leadsto a port which is connected to the air-exhaust pipe 13. A port 18 isfor connecting the control pipe 9.

The auxiliary valve 10 has a closure member 19 which is adapted to bescrewed into a sleeve 20 and is biased by a spring 21. The air-exhaustvalve is similarly constructed; it has a closure member 22 which isadapted to be screwed into a sleeve 23 and may be biased by a spring 24.The valves are guided in inserts 25 and 26. The two valves are actuatedby a doublearmed lever 27 which is adapted to swing about a pivotalpoint 28 solid with the casing. One end 29 of the lever, after passingthrough a lost-motion phase, is enabled to engage a drive face 30 on thesleeve 20, while the end 31 of the lever engages a drive face 32 on thesleeve 23. By altering the position of the sleeves 20 or 23 the lostmotion and the valve setting can be adjusted.

The lever 27 extends through a slot 33 in an actuating element 34 and isdriven by two pins 35 and 36 extending through the slot. The lower endof the actuating element is provided with a pin 37 which extends througha gland 38 and is provided at its outer end with a dished element 39.Against the dished element there presses a rated-value spring 40 whichis accommodated in a casing attachment 41 and can be set to apredetermined value with the help of a hand wheel 42, a screw 43 and ascrew-on backing element 44. The spring 40 is enabled to press a collar45 on the actuating element 34 against a sleeve 46 which is adapted tobe screwed into the casing 15. The inoperative position of the valvecombination can be set with the help of this sleeve. In this inoperativeposition the double-armed lever 27 should hold the air-exhaust valve 14open.

At the upper end of the actuating element 34 there engages a diaphragm49 of a pressure unit 50, a distance sleeve 47 and a pressure cap 48being interposed between the actuating element and the diaphragm. Thepressure unit is connected to a temperature sensor 52 by way of acapillary tube 51. The sensing system contains CO for example and, inthe sensor, an absorption medium in the form of activated carbon. Theupper end of the actuating element 34 and the distance sleeve 47 aresurrounded by a bellows 53 which tightly seals off the space 54accommodating the actuating element. The bellows is surrounded by anattachment 55 which together with the bellows and the diaphragm definesa chamber 56 sealed off against the exterior. This chamber is filledwith a dry gas which has a lower pressure than atmospheric pressure. Ifonly a very slight quantity of gas is present, the chamber can beregarded as being evacuated.

When the temperature in the cold compartment rises the pressure in thepressure unit 50 increases. The actuating element 34 is moved downwards.The air-exhaust valve 14 closes and then the auxiliary valve 10 opens.Nitrogen vapour 5 then flows into the control pipe 9. The high pressurealso affects the space 54. Hoever since this space has only a smallcross-sectional area in comparison with the diaphragm 49, interferenceis slight. In the chamber 56 there obtains a constant pressure which canbe easily taken into acount during adjustment. If the temperature dropsat a later stage, first the auxiliary valve 10 closes whereupon theair-exhaust valve 14 opens.

The main valve 7 illustrated in FIG. 3 has a casing 61 with an inletport 62 and an outlet port 63. It is secured by means of screws 64. Avalve spindle 65 is held in a guide 66 solid with the casing. Theclosure member 67 cooperates with the valve seat 68. The spindle 65 isacted upon at one end by a spring 69 and by a diaphragm 71 at the otherend, a pressure cap 70 being fitted between the spindle and thediaphragm which is part of a pressure unit 72. The control pipe 9 isconnected to the port of this pressure unit.

The upper part of the spindle 65 is surrounded by a bellows 73 so that aspace 74 is formed which communicates with the outlet side of theworking chamber of the valve. The casing together with the diaphragm 71and the bellows 73 forms a chamber 75. This chamber 75 is substantiallysealed off against the surrounding atmosphere. It is located along aflow-resisting passage which consists of the sections 76 and 77. Insection 76 the flow-restricting action is greater than in section 77.The valve 7 is normally closed. The pressure in the compartment 2 thenobtains in the workin chamber of the valve, in the passage sections 76and 77 and in the chamber 75. It is also possible for atmospheric air topass through section 77 of the passage and into the chamber 75. Ifnitrogen vapour is passed to the pressure unit 72 by way of the controlvalve 9, the valve 7 opens fully and supplies liquid nitrogen to all thenozzles 8a. A very small quantity of nitrogen flows out through thepassage sections 76 and 77. During the flow-restricting action thenitrogen vaporizes and carries any moisture out of the chamber 75. Thepressure-drop at the flow-restricting point 76 results in so low apressure in the chamber 75 that the control is not noticeably influencedby the pressure in the pressure unit 72. The same purpose is served bythe bellows 74 having a cross-sectional area which is only aboutonetwelfth of the area of the diaphragm.

It is not necessary for the valves 10 and 14 to be combined in a singleunit and to be operated by a single actuating element. Instead,individual valves can be used and operated in opposite directionsthrough stepping lines.

I claim:

1. A valve assembly for a cooling system comprising a container forstoring a refrigerant under pressure, main valve means and firstauxiliary valve means connected to said container, pressure operatedvalve operating means connected to said main valve means, main conduitmeans between said pressure operated valve operating means and saidfirst auxiliary valve means, branch conduit means extending from saidmain conduit means for venting said main conduit means, second auxiliaryvalve means in said branch conduit means for controlling said venting,temperature responsive means for actuating said first and secondauxiliary valve means, said auxiliary valve means including a commondouble armed lever for displacing said first and second auxiliary valvemeans in opposite directions, said first and second auxiliary valvemeans having overlapping ranges and being oppositely actuatable so thatone is fully opened when the other is fully closed and vice versa.

1. A valve assembly for a cooling system comprising a container forstoring a refrigerant under pressure, main valve means and firstauxiliary valve means connected to said container, pressure operatedvalve operating means connected to said main valve means, main conduitmeans between said pressure operated valve operating means and saidfirst auxiliary valve means, branch conduit means extending from saidmain conduit means for venting said main conduit means, second auxiliaryvalve means in said branch conduit means for controlling said venting,temperature responsive means for actuating said first and secondauxiliary valve means, said auxiliary valve means including a commondouble armed lever for displacing said first and second auxiliary valvemeans in opposite directions, said first and second auxiliary valvemeans having overlapping ranges and being oppositely actuatable so thatone is fully opened when the other is fully closed and vice versa.